Any combustion can create CO given the right (or wrong) circumstances -- a low oxygen environment. Hydrogen is the only one that shouldn't, at least in theory; though IIRC very hot objects in contact with air are known to give off small amounts of CO directly.

Many CO detectors won't work properly below a certain temperature. Read the specs before relying on one.

Ventilation is always needed, not only to keep the oxygen level up but to vent out some of the moisture. Moisture kills insulation, and the amount you breathe out is surprising.

I've always carried a stash of candles in the car with appropriate containers. If they are tea lights, I carry a bit of extra wick or twine to make them burn a bit hotter on demand. I'm leery of an open pot of flammable liquid in such tight quarters: one jostle as I'm dozing and I can turn my emergency shelter into a smoke-filled mess. Yikes.